使用PyCrypto AES-256加密和解密

我试图使用PyCrypto构建两个函数，它们接受两个参数:消息和密钥，然后加密/解密消息。

我在网上找到了几个链接来帮助我，但每一个都有缺陷:

这个在codekoala使用os。这是PyCrypto不鼓励的。

此外，我给函数的键不能保证具有预期的确切长度。我要怎么做才能做到呢?

还有，有几种模式，推荐哪种模式?我不知道用什么:/

最后，4到底是什么?我是否可以提供不同的IV来加密和解密，或者这将返回不同的结果?

588848 次浏览
小开

你可以通过使用加密哈希函数(不 Python内置的hash)，如SHA-1或SHA-256，从任意密码中获得密码短语。Python在其标准库中包含了对这两者的支持:

import hashlib


hashlib.sha1("this is my awesome password").digest() # => a 20 byte string
hashlib.sha256("another awesome password").digest() # => a 32 byte string

你可以通过使用[:16]或[:24]截断一个加密哈希值，它将保留其安全性直到你指定的长度。

小开

你可能需要以下两个函数:pad-填充(加密时)和unpad- unpad(解密时)，当输入长度不是BLOCK_SIZE的倍数时。

BS = 16
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[:-ord(s[len(s)-1:])]

你问的是键的长度?你可以使用键的MD5哈希值，而不是直接使用它。

而且，根据我使用PyCrypto的一点经验，当输入相同时，IV用于混合加密的输出，因此IV被选择为随机字符串，并将其用作加密输出的一部分，然后使用它来解密消息。

这是我的实现:

import base64
from Crypto.Cipher import AES
from Crypto import Random


class AESCipher:
def __init__( self, key ):
self.key = key


def encrypt( self, raw ):
raw = pad(raw)
iv = Random.new().read( AES.block_size )
cipher = AES.new( self.key, AES.MODE_CBC, iv )
return base64.b64encode( iv + cipher.encrypt( raw ) )


def decrypt( self, enc ):
enc = base64.b64decode(enc)
iv = enc[:16]
cipher = AES.new(self.key, AES.MODE_CBC, iv )
return unpad(cipher.decrypt( enc[16:] ))
小开

为了其他人的利益，这里是我的解密实现，我通过组合@Cyril和@Marcus的答案得到的。这假设它是通过HTTP请求传入的，加密文本加引号，base64编码。

import base64
import urllib2
from Crypto.Cipher import AES




def decrypt(quotedEncodedEncrypted):
key = 'SecretKey'


encodedEncrypted = urllib2.unquote(quotedEncodedEncrypted)


cipher = AES.new(key)
decrypted = cipher.decrypt(base64.b64decode(encodedEncrypted))[:16]


for i in range(1, len(base64.b64decode(encodedEncrypted))/16):
cipher = AES.new(key, AES.MODE_CBC, base64.b64decode(encodedEncrypted)[(i-1)*16:i*16])
decrypted += cipher.decrypt(base64.b64decode(encodedEncrypted)[i*16:])[:16]


return decrypted.strip()
小开
最佳答案

下面是我的实现，它通过一些修复为我工作。它将密钥和秘密短语的对齐增强为32字节，IV为16字节:

import base64
import hashlib
from Crypto import Random
from Crypto.Cipher import AES


class AESCipher(object):


def __init__(self, key):
self.bs = AES.block_size
self.key = hashlib.sha256(key.encode()).digest()


def encrypt(self, raw):
raw = self._pad(raw)
iv = Random.new().read(AES.block_size)
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return base64.b64encode(iv + cipher.encrypt(raw.encode()))


def decrypt(self, enc):
enc = base64.b64decode(enc)
iv = enc[:AES.block_size]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return self._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')


def _pad(self, s):
return s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs)


@staticmethod
def _unpad(s):
return s[:-ord(s[len(s)-1:])]
小开

对于想要使用urlsafe_b64encode和urlsafe_b64decode的人，这里是为我工作的版本(在花了一些时间与unicode问题之后)

BS = 16
key = hashlib.md5(settings.SECRET_KEY).hexdigest()[:BS]
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[:-ord(s[len(s)-1:])]


class AESCipher:
def __init__(self, key):
self.key = key


def encrypt(self, raw):
raw = pad(raw)
iv = Random.new().read(AES.block_size)
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return base64.urlsafe_b64encode(iv + cipher.encrypt(raw))


def decrypt(self, enc):
enc = base64.urlsafe_b64decode(enc.encode('utf-8'))
iv = enc[:BS]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return unpad(cipher.decrypt(enc[BS:]))
小开 
from Crypto import Random
from Crypto.Cipher import AES
import base64


BLOCK_SIZE=16
def trans(key):
return md5.new(key).digest()


def encrypt(message, passphrase):
passphrase = trans(passphrase)
IV = Random.new().read(BLOCK_SIZE)
aes = AES.new(passphrase, AES.MODE_CFB, IV)
return base64.b64encode(IV + aes.encrypt(message))


def decrypt(encrypted, passphrase):
passphrase = trans(passphrase)
encrypted = base64.b64decode(encrypted)
IV = encrypted[:BLOCK_SIZE]
aes = AES.new(passphrase, AES.MODE_CFB, IV)
return aes.decrypt(encrypted[BLOCK_SIZE:])
小开

您可以使用类似PKCS#7填充的方案。您可以使用它来代替前面的函数来填充(进行加密时)和解封(进行解密时)。我将在下面提供完整的源代码。

import base64
import hashlib
from Crypto import Random
from Crypto.Cipher import AES
import pkcs7


class Encryption:


def __init__(self):
pass


def Encrypt(self, PlainText, SecurePassword):
pw_encode = SecurePassword.encode('utf-8')
text_encode = PlainText.encode('utf-8')


key = hashlib.sha256(pw_encode).digest()
iv = Random.new().read(AES.block_size)


cipher = AES.new(key, AES.MODE_CBC, iv)
pad_text = pkcs7.encode(text_encode)
msg = iv + cipher.encrypt(pad_text)


EncodeMsg = base64.b64encode(msg)
return EncodeMsg


def Decrypt(self, Encrypted, SecurePassword):
decodbase64 = base64.b64decode(Encrypted.decode("utf-8"))
pw_encode = SecurePassword.decode('utf-8')


iv = decodbase64[:AES.block_size]
key = hashlib.sha256(pw_encode).digest()


cipher = AES.new(key, AES.MODE_CBC, iv)
msg = cipher.decrypt(decodbase64[AES.block_size:])
pad_text = pkcs7.decode(msg)


decryptedString = pad_text.decode('utf-8')
return decryptedString


import StringIO
import binascii




def decode(text, k=16):
nl = len(text)
val = int(binascii.hexlify(text[-1]), 16)
if val > k:
raise ValueError('Input is not padded or padding is corrupt')


l = nl - val
return text[:l]




def encode(text, k=16):
l = len(text)
output = StringIO.StringIO()
val = k - (l % k)
for _ in xrange(val):
output.write('%02x' % val)
return text + binascii.unhexlify(output.getvalue())
小开

这是另一种观点(主要源自上述解决方案)，但是

  • 使用null填充
  • 不使用lambda(从来不是粉丝)

  • 测试python 2.7和3.6.5

    #!/usr/bin/python2.7
# you'll have to adjust for your setup, e.g., #!/usr/bin/python3




import base64, re
from Crypto.Cipher import AES
from Crypto import Random
from django.conf import settings


class AESCipher:
"""
Usage:
aes = AESCipher( settings.SECRET_KEY[:16], 32)
encryp_msg = aes.encrypt( 'ppppppppppppppppppppppppppppppppppppppppppppppppppppppp' )
msg = aes.decrypt( encryp_msg )
print("'{}'".format(msg))
"""
def __init__(self, key, blk_sz):
self.key = key
self.blk_sz = blk_sz


def encrypt( self, raw ):
if raw is None or len(raw) == 0:
raise NameError("No value given to encrypt")
raw = raw + '\0' * (self.blk_sz - len(raw) % self.blk_sz)
raw = raw.encode('utf-8')
iv = Random.new().read( AES.block_size )
cipher = AES.new( self.key.encode('utf-8'), AES.MODE_CBC, iv )
return base64.b64encode( iv + cipher.encrypt( raw ) ).decode('utf-8')


def decrypt( self, enc ):
if enc is None or len(enc) == 0:
raise NameError("No value given to decrypt")
enc = base64.b64decode(enc)
iv = enc[:16]
cipher = AES.new(self.key.encode('utf-8'), AES.MODE_CBC, iv )
return re.sub(b'\x00*$', b'', cipher.decrypt( enc[16:])).decode('utf-8')
小开

让我来回答你关于“模式”的问题。aes - 256是一种分组密码。它接受一个32字节的关键和一个称为块的16字节字符串作为输入，并输出一个块。为了加密，我们在操作模式中使用AES。上面的解决方案建议使用加拿大广播公司，这是一个例子。另一个被称为CTR，它更容易使用:

from Crypto.Cipher import AES
from Crypto.Util import Counter
from Crypto import Random


# AES supports multiple key sizes: 16 (AES128), 24 (AES192), or 32 (AES256).
key_bytes = 32


# Takes as input a 32-byte key and an arbitrary-length plaintext and returns a
# pair (iv, ciphtertext). "iv" stands for initialization vector.
def encrypt(key, plaintext):
assert len(key) == key_bytes


# Choose a random, 16-byte IV.
iv = Random.new().read(AES.block_size)


# Convert the IV to a Python integer.
iv_int = int(binascii.hexlify(iv), 16)


# Create a new Counter object with IV = iv_int.
ctr = Counter.new(AES.block_size * 8, initial_value=iv_int)


# Create AES-CTR cipher.
aes = AES.new(key, AES.MODE_CTR, counter=ctr)


# Encrypt and return IV and ciphertext.
ciphertext = aes.encrypt(plaintext)
return (iv, ciphertext)


# Takes as input a 32-byte key, a 16-byte IV, and a ciphertext, and outputs the
# corresponding plaintext.
def decrypt(key, iv, ciphertext):
assert len(key) == key_bytes


# Initialize counter for decryption. iv should be the same as the output of
# encrypt().
iv_int = int(iv.encode('hex'), 16)
ctr = Counter.new(AES.block_size * 8, initial_value=iv_int)


# Create AES-CTR cipher.
aes = AES.new(key, AES.MODE_CTR, counter=ctr)


# Decrypt and return the plaintext.
plaintext = aes.decrypt(ciphertext)
return plaintext


(iv, ciphertext) = encrypt(key, 'hella')
print decrypt(key, iv, ciphertext)

这通常被称为AES-CTR。我建议谨慎使用AES-CBC与PyCrypto。原因是它需要你指定填充方案，正如给出的其他解决方案所示。一般来说，如果你不是非常，小心填充，有攻击完全破坏加密! .

现在，重要的是要注意键必须是随机的32字节字符串;密码不就足够了。通常，键的生成是这样的:

# Nominal way to generate a fresh key. This calls the system's random number
# generator (RNG).
key1 = Random.new().read(key_bytes)

键也可以是从密码派生:

# It's also possible to derive a key from a password, but it's important that
# the password have high entropy, meaning difficult to predict.
password = "This is a rather weak password."


# For added # security, we add a "salt", which increases the entropy.
#
# In this example, we use the same RNG to produce the salt that we used to
# produce key1.
salt_bytes = 8
salt = Random.new().read(salt_bytes)


# Stands for "Password-based key derivation function 2"
key2 = PBKDF2(password, salt, key_bytes)
上面的一些解决方案建议使用sha - 256来派生键，但这通常被认为是糟糕的密码实践。 查阅维基百科获取更多关于操作模式的信息
小开

我很感激其他启发我的答案，但它们对我不起作用。

在花了几个小时试图弄清楚它是如何工作的之后，我用最新的PyCryptodomex库提出了下面的实现(这是另一个故事，我如何设法在代理后设置它，在Windows上，在virtualenv…唷)

它正在处理您的实现。记得写下填充、编码和加密步骤(反之亦然)。你必须打包和拆包，记住顺序。

import base64
import hashlib
from Cryptodome.Cipher import AES
from Cryptodome.Random import get_random_bytes


__key__ = hashlib.sha256(b'16-character key').digest()


def encrypt(raw):
BS = AES.block_size
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)


raw = base64.b64encode(pad(raw).encode('utf8'))
iv = get_random_bytes(AES.block_size)
cipher = AES.new(key= __key__, mode= AES.MODE_CFB,iv= iv)
return base64.b64encode(iv + cipher.encrypt(raw))


def decrypt(enc):
unpad = lambda s: s[:-ord(s[-1:])]


enc = base64.b64decode(enc)
iv = enc[:AES.block_size]
cipher = AES.new(__key__, AES.MODE_CFB, iv)
return unpad(base64.b64decode(cipher.decrypt(enc[AES.block_size:])).decode('utf8'))
小开

看到mnothic的回答。

兼容UTF-8编码:

def _pad(self, s):
s = s.encode()
res = s + (self.bs - len(s) % self.bs) * chr(self.bs - len(s) % self.bs).encode()
return res
小开

我已经使用了Crypto和PyCryptodomex库，它是极快的…

import base64
import hashlib
from Cryptodome.Cipher import AES as domeAES
from Cryptodome.Random import get_random_bytes
from Crypto import Random
from Crypto.Cipher import AES as cryptoAES


BLOCK_SIZE = AES.block_size


key = "my_secret_key".encode()
__key__ = hashlib.sha256(key).digest()
print(__key__)


def encrypt(raw):
BS = cryptoAES.block_size
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
raw = base64.b64encode(pad(raw).encode('utf8'))
iv = get_random_bytes(cryptoAES.block_size)
cipher = cryptoAES.new(key= __key__, mode= cryptoAES.MODE_CFB,iv= iv)
a= base64.b64encode(iv + cipher.encrypt(raw))
IV = Random.new().read(BLOCK_SIZE)
aes = domeAES.new(__key__, domeAES.MODE_CFB, IV)
b = base64.b64encode(IV + aes.encrypt(a))
return b


def decrypt(enc):
passphrase = __key__
encrypted = base64.b64decode(enc)
IV = encrypted[:BLOCK_SIZE]
aes = domeAES.new(passphrase, domeAES.MODE_CFB, IV)
enc = aes.decrypt(encrypted[BLOCK_SIZE:])
unpad = lambda s: s[:-ord(s[-1:])]
enc = base64.b64decode(enc)
iv = enc[:cryptoAES.block_size]
cipher = cryptoAES.new(__key__, cryptoAES.MODE_CFB, iv)
b=  unpad(base64.b64decode(cipher.decrypt(enc[cryptoAES.block_size:])).decode('utf8'))
return b


encrypted_data =encrypt("Hi Steven!!!!!")
print(encrypted_data)
print("=======")
decrypted_data = decrypt(encrypted_data)
print(decrypted_data)
小开

使用AES-256和utf8mb4加密和解密拉丁字符和特殊字符(中文):

对于那些需要加密和解密拉丁文和特殊值(如中文)的人，这里有一个@MIkee代码的修改来完成这个任务。

记住，UTF-8本身不能处理这种类型的编码。

import base64, re
from Crypto.Cipher import AES
from Crypto import Random
from django.conf import settings


import codecs


# Make utf8mb4 recognizable.
codecs.register(lambda name: codecs.lookup('utf8') if name == 'utf8mb4' else None)




class AESCipher:


def __init__(self, key, blk_sz):
self.key = key
self.blk_sz = blk_sz


def encrypt( self, raw ):
# raw is the main value
if raw is None or len(raw) == 0:
raise NameError("No value given to encrypt")
raw = raw + '\0' * (self.blk_sz - len(raw) % self.blk_sz)
raw = raw.encode('utf8mb4')
# Initialization vector to avoid same encrypt for same strings.
iv = Random.new().read( AES.block_size )
cipher = AES.new( self.key.encode('utf8mb4'), AES.MODE_CFB, iv )
return base64.b64encode( iv + cipher.encrypt( raw ) ).decode('utf8mb4')


def decrypt( self, enc ):
# enc is the encrypted value
if enc is None or len(enc) == 0:
raise NameError("No value given to decrypt")
enc = base64.b64decode(enc)
iv = enc[:16]
# AES.MODE_CFB that allows bigger length or Latin values
cipher = AES.new(self.key.encode('utf8mb4'), AES.MODE_CFB, iv )
return re.sub(b'\x00*$', b'', cipher.decrypt( enc[16:])).decode('utf8mb4')

用法:

>>> from django.conf import settings
>>> from aesencryption import AESCipher
>>>
>>> aes = AESCipher(settings.SECRET_KEY[:16], 32)
>>>
>>> value = aes.encrypt('漢字')
>>>
>>> value
'hnuRwBjwAHDp5X0DmMF3lWzbjR0r81WlW9MRrWukgQwTL0ZI88oQaWvMfBM+W87w9JtSTw=='
>>> dec_value = aes.decrypt(value)
>>> dec_value
'漢字'
>>>

拉丁字母也是如此，比如ã, á, à, â, ã, ç等等。

注意点

请记住，如果要在数据库中存储拉丁值，则需要将其设置为允许这种类型的数据。因此，如果你的数据库被设置为utf - 8，它将不接受这种类型的数据。你也需要在那里换衣服。

小开

你可以使用新的django-mirage-field包。

小开

PyCrypto已经过时了。

密码学现在有更好的支持。

这是另一个实现。注意，这将返回字节，您需要使用base64将它们转换为用于传输的字符串。

import os
import hashlib
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend


_BLOCK_SIZE = 16


class AesStringCipher:
def __init__(self, key):
self._key = hashlib.sha256(key.encode()).digest()


def encrypt_str(self, raw:str) -> bytes:
iv = os.urandom(_BLOCK_SIZE)
cipher = Cipher(algorithms.AES(self._key), modes.CBC(iv), default_backend())
encryptor = cipher.encryptor()
raw = _pad(raw)
return iv + encryptor.update(raw.encode('utf-8')) + encryptor.finalize()


def decrypt_str(self, enc:bytes) -> str:
iv = enc[:_BLOCK_SIZE]
enc = enc[_BLOCK_SIZE:]
cipher = Cipher(algorithms.AES(self._key), modes.CBC(iv), default_backend())
decryptor = cipher.decryptor()
raw = decryptor.update(enc) + decryptor.finalize()
raw = raw.decode('utf-8')
return _unpad(raw)


def _pad(s:str) -> str:
padding = (_BLOCK_SIZE - (len(s) % _BLOCK_SIZE))
return s + padding * chr(padding)


def _unpad(s:str) -> str:
return s[:-ord(s[len(s)-1:])]




if __name__ == '__main__':
cipher = AesStringCipher('my secret password')


secret_msg = 'this is a super secret msg ...'
enc_msg = cipher.encrypt_str(secret_msg)
dec_msg = cipher.decrypt_str(enc_msg)


assert secret_msg == dec_msg

提交答案